"Focus" problem that is driving me insane

[Edwin Beckenbach]

Also, f32 is a perfectly appropriate aperture for a 90mm lens with a good deal of rise. You could probably get away with f22 but f11 would really be pushing it in terms of aberrations in the corners and much smaller tolerances in the film plane positioning.

Edit: I just reread and see you used 135mm not 90mm. I'd still recommend f22, possibly f16.

[engl]

Thanks for the diffraction information. Incredibly, I wasn't aware of it.
Down to f11 I go.

Keep in mind that shooting at F11 makes the problem even worse. At wider apertures, smaller shifts of the film are enough to result in blur. It also puts stricter requirements on the film being flat and at precisely the right registration distance (not the case with all holders and backs). Apart from this, it is obviously also more difficult to get all critical parts of the shot into perfect focus on the GG, especially if the camera is not rigid and easily adjusted.

F32 will start showing diffraction printed big, and push exposure times to where you might get color shifts due to reciprocal failure during night shooting (reciprocal failure also results in slightly lower dynamic range). With a scene not requiring small apertures to get everything focused (sometimes you just need F45), I'd go with F16-F22, and use the methods described in this thread to avoid "film pop".

[Vaughn]

I get film pop with long exposures under the redwoods (often 10 secs to 30 minutes). And sometimes it is film slippage rather than popping (the film sitting slightly crooked in the holder, than falling into place during the exposure -- this leaves one corner sharp and a double exposure showing more and more as one works to the opposite corner. I give the holder a good tap on the palm of my hand, now, before I load the holder into the camera.

I tried a piece of two-sided tape in the holder, but it just made loading and unloading more difficult and would leave tape residue on the back of the film (interfering with the removal of the anti-halation layer.)

[Arne Croell]

As for your question why the Quickloads were better, remember that the Quickload/Readyload holders employ a pressure plate. That would hold the film at three edges, and the 4th top edge is stabilized by the plastic sheet connected to the film. Regular holders with pressure plates are the Sinar 4x5 Precision film holder (one sheet/holder only), or the older thicker Linhof film and plate holders. The latter used the pressure plate not for stabilizing the film but to allow the use of glass plates in there and grasp the film only on two edges whereas the Sinar holder holds it on all four edges. Both are out of production and were expensive, but can be found used sometimes. Note that a pressure plate is not a guarantee for not popping - if the emulsion side expands, e.g. because of a higher humidity, it could pop out in the center. One would need a larger humidity change for movement with a pressure plate than without, though. The better one of those two for you would be the Sinar Precision holder.
Btw, I think humidity is much more of a point than temperature on its own (of course a temperature change is often associated with a humidity change); imagine the film in the holder being suddenly exposed to a different humidity, the absorption or desorption of water vapor will be much faster in the emusion on the front side than in the anti-curling layer on the back side because the latter is next to the holder wall, leading to a temporary curl or pop.
The best solution would be a vacuum holder like the ones used in aerial cameras or the short-lived Schneider system in the late 1990's, but those would be hard to get.

[BetterSense]

I would imagine a Grafmatic might also help with film popping.

[Joseph O'Neil]

I would go with "film pop" too. Way back in the days when dinosaurs walked the earth, and guys used to still use film for astro-photography, "film-pop- was a common problem for long exposures in cameras, even 35mm at the time.

Solutions back then ranged from drilling and tapping a camera body to run dry nitrogen in during a long exposure (for everything form 35mm to 4x5), make a custom 4x5 film holder that had tiny holes and hooked to a vacuum of some kind to hold the film in place - but that had problems too.

You see, to harsh a vacuum, and it would warp the film too, so believe it or not, a breast pump of all things provided the exact right amount of suction needed to hold the film in place and not warp it. Seriously, if you think it sounds weird, imagine some night watching 50 grand worth of optics, computers and mechanics all working in unison, with a playtex breast pump duct taped to the side of a tripod leg.

The other classic answer was plain old fashioned glass plates, but you cannot get those anymore either I believe.

However, I do have a solution that should work, if you can find one. Hunt high and low and buy yourself a used Linhof spring loaded film holder. Not perfect, but pretty darned good, just hard as heck to find them used anymore.

One last thought, for what it is worth, I find if I shoot landscape instead of portrait, film pop is less over long exposures, However that really limits you in some cases.

good luck
joe

[Bob Salomon]

"However, I do have a solution that should work, if you can find one. Hunt high and low and buy yourself a used Linhof spring loaded film holder. Not perfect, but pretty darned good, just hard as heck to find them used anymore. "

Afraid that this would be no better then the regular, and also discontinued, Linhof Double Sheet Film Holders.

What you recommended were the Linhof Glass Plate/Sheet Film Holders. Since these could use either a thick glass plate or a thin sheet of film. To adjust to both they had a spring loaded plate. But this was not a pressure plate and did not hold film any flatter then the Linhof Sheet Film Holders. They would just be thicker and heavier then what would be needed.
Lastly, unlike a roll or 35mm camera, there are no film rails to position the film against in a sheet film holder so the spring adjustment plate in the Linhof Glass Plate Holder has nothing to push the film against to hold it flat. Just like any other sheet film holder without either a vacuum or adhesive the film can still sag forward in the holder.

Film holder for sheet film that do not let film sag were either vacuum holders like the Hoffmann or the short lived Linhof Vacuum Sheet Film Holders or the Linhof 5" Vacuum Roll Back for the Aero Technika and the Technika or adhesive holders like the Sinar and the short lived Schneider holder.

[Brian Ellis]

At f32 you are in diffraction. What happens at f22 or f16?

The effect of diffraction would show up as an overall "softness" of the image, it wouldn't cause only part of the image to be unsharp while other parts are sharp.

Tobasco, your technique sounds fine. I'd check for film "pop" as many others have stated and also a bellows or lens board leak. I had a lens board from which a cable release gizmo had been removed, leaving a small hole in the board. I foolishly didn't think to cover the hole and the resulting photographs looked a lot like what you're posting. So it's probably a long shot but worth checking.

[Arne Croell]

"
Film holder for sheet film that do not let film sag were either vacuum holders like the Hoffmann or the short lived Linhof Vacuum Sheet Film Holders or the Linhof 5" Vacuum Roll Back for the Aero Technika and the Technika or adhesive holders like the Sinar and the short lived Schneider holder.

Only the larger Sinar holders used sticky tape. The 4x5" Sinar Precision holder used a pressure plate and clamped the film on all 4 sides.
And the Schneider holder was a vacuum holder not an adhesive one.

[Doremus Scudder]

I'm voting (strongly) for film pop/slippage as well. Not only does this happen to me on long exposures semi-regularly (irritatingly so) but none of the other possible causes you mention explain the double-image in the blurry area. It's definitely film movement and not diffraction (which would show up over the entire image). If things look equally sharp over the entire ground glass when you are focusing, then it's not bad focus either unless your ground glass is not aligned properly. If you only have this problem with night shots. Bet on the obvious. (But do check to make sure your compressed bellows isn't pushing the lens out of alignment before the shot is taken.)

Some tips to prevent the slip/pop problem: 1: Before inserting the film holder, rap its bottom sharply on the palm of your hand in exactly the orientation it will go into the camera. This will "seat" the film sheet and keep it from slipping down during exposure. 2: Pull the darkslide and wait 30 seconds or so before opening the shutter. This gives the film a chance to adjust to the temperature and humidity inside the camera and pop to a more stable position. This is especially important when you keep you holders in plastic bags at different ambient temps (as most all of us do). 3. Make safety backups of important shots. If you get 30% error like this, then this will increase your chances of a good exposure.

Forget looking elsewhere till you have done the above.

Best and good shooting.


Doremus Scudder